Because my old machine did not have either Error.pm or Algorithm::Diff, /bin/configure would report that TWiki.pm was not found in @INC. The issue was that TWiki.pm or some related function could not be compiled.

/bin/configure does some checking of it's own... Maybe it could check for the required modules there and report to the user if any are missing? (I did install one or two modules based on configure's recommendation, but it didn't mention Error.pm or Algorithm::Diff)